RDMA/hns: Limit the length of data copied between kernel and userspace

For ib_copy_from_user(), the length of udata may not be the same as that
of cmd. For ib_copy_to_user(), the length of udata may not be the same as
that of resp. So limit the length to prevent out-of-bounds read and write
operations from ib_copy_from_user() and ib_copy_to_user().

Fixes: de77503a ("RDMA/hns: RDMA/hns: Assign rq head pointer when enable rq record db")
Fixes: 633fb4d9 ("RDMA/hns: Use structs to describe the uABI instead of opencoding")
Fixes: ae85bf92 ("RDMA/hns: Optimize qp param setup flow")
Fixes: 6fd610c5 ("RDMA/hns: Support 0 hop addressing for SRQ buffer")
Fixes: 9d9d4ff7 ("RDMA/hns: Update the kernel header file of hns")
Link: https://lore.kernel.org/r/1607650657-35992-2-git-send-email-liweihang@huawei.com


Signed-off-by: Wenpeng Liang <liangwenpeng@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>